Scientists found that different beak shapes correlate with different mating songs in Darwin's finches. Which hypothesis does this support?

Question

A.  Darwin's finches are not different species according to the Biological Species Concept.
B.  Adaptation to different food sources led to behavioral isolation in Darwin's finches.
C.  Mating songs are primarily determined by the acoustics of different beaks.
D.  Adaptation to different food sources likely occurred after reproductive isolation in Darwin's finches.


Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?

  Gather Content
· What do you already know about reproductive isolation?
 
Choose Answer· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

  Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

B.  Adaptation to different food sources led to behavioral isolation in Darwin's finches.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses reproductive isolation.
· What type of thinking is required?
        o This question is asking you to weigh and judge evidence, or evaluate, to choose the best of the possible answers.

  Gather Content
· What do you already know about reproductive isolation?
        o Populations are considered to be different species when the members are reproductively isolated from each other.
        o Reproductive isolating mechanisms prevent genetic exchange between species. Some prevent the formation of zygotes – prezygotic isolating mechanisms. Others prevent the proper functioning of zygotes after they form – postzygotic isolating mechanisms.
        o Prezygotic isolating mechanisms include ecological isolation, behavioral isolation, temporal isolation, mechanical isolation, and prevention of gamete fusion.
        o Ecological isolation happens when two species occur in the same area, but use different portions of the environment and thus do not hybridize.
        o Behavioral isolation is when related species differ in their courtship rituals, keeping these species distinct.
        o Temporal isolation is when species reproduce in different seasons.
        o Mechanical isolation is when the morphology of two species prevents mating.
        o Sometimes gametes cannot fuse properly even when they meet.
        o Postzygotic isolation occurs when hybrids between species are either inviable (poor at surviving) or infertile (unable to reproduce themselves).
 
Choose Answer· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Is it likely that Darwin's finches are not different species according to the biological species concept? No. The biological species concept defines species as groups which are reproductively isolated. Having different mating songs is a mechanism of reproductive isolation.
        o Is it likely that mating songs are primarily determined by the acoustics of different beaks? No, this doesn’t seem likely. Mating songs vary mostly in the pattern and tempo of the notes – a feature of brain circuits, not the beak.
        o Is it likely that adaptation to different food sources occurred after reproductive isolation in Darwin's finches? Not likely. Reproductive isolation wouldn’t necessarily encourage two new species to diverge in their food preferences. However, different food preferences CAN set the stage for reproductive isolation to follow.
        o Is it likely that adaptation to different food sources led to behavioral isolation in Darwin's finches? Yes. Having different niches – ecological isolation – limits the hybridization of two groups, causing reproductive isolation, and further behavioral isolation due to changes in mating songs.

  Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o The question required you to weigh and judge evidence, or evaluate, to choose the best of the possible answers.
        o Did you recognize that preferences for different foods can lead to ecological isolation, which allows development of behavioral isolation barriers?